In general, a washing machine performs washing by rotating a drum having laundries therein through a driving force transmitted by a motor in a state where detergent and the laundry are mixedly loaded into a drum.
A drum washing machine which has been preferably used recently in the related art will be embodied as follows.
The drum washing machine is classified by a driving method into an indirect-motor-drive type and a direct-motor drive type. According to the indirect-motor-drive type washing machine, the driving force of motor is indirectly transmitted to a drum through a motor pulley and a belt wound around a drum pulley. According to the direct-motor-drive type drum washing machine, the driving fore of motor is directly transmitted to a drum, because a rotor of a BLDC motor is directly connected with the drum.
Referring to FIG. 1, a conventional direct-drive motor type drum washing machine will be schematically described.
FIG. 1 is a longitudinal sectional view illustrating a structure of a conventional drum washing machine. The conventional drum washing machine includes a cabinet 1 defining an exterior thereof, a tub 2 mounted within the cabinet 1 with a front side opened and a drum 3 rotatably mounted in an inner center of the tub 2.
Moreover, a motor 47 having a stator 6 and a rotor 5 are mounted in a rear wall of the tub 2. The stator 6 is secured to the rear wall of the tub 2, and the rotor 5 passes through the tub 2 surrounding the stator 6 and is connected with the drum 3 by a shaft 4.
Together with that, a tub supporter in the same appearance as an exterior of the rear wall of the tub 2 is provided between the rear wall of the tub 2 and the stator 6, and fastened to the rear wall of the tub 2 to support the load of the stator 6 when fastening the stator 6. Also, the tub supporter is made of metal to maintain the concentricity of the stator 6.
Meanwhile, a door 21 is coupled to a front side of the cabinet 1, and a gasket 22 is provided between the door 21 and the tub 2.
In addition, a hanging spring 23 is provided between an upper inner surface of the cabinet 1 and an upper circumferential surface of the tub 2 to support the tub 2. Also, a friction damper 24 is provided between an inner lower surface of the cabinet 1 and a lower portion of the outer circumferential surface of the tub 2 to dampen the vibration of tub 2 generated in spinning.
Referring to FIG. 2, a bearing housing 7 having a hollow 55 formed in a center thereof is inserted into the tub 2. The shaft 4 of the motor 47 passes through the hollow 55.
At that time, the bearing housing 7 is made of aluminum alloy and formed as one body with the rear wall of the tub 2 by being inserted into the rear wall of the tub 2 when injection-molding the tub 2 with plastic resin.
As shown in FIG. 2, the rear wall of the tub 2 has plural ribs 201 formed on the same diameter inwardly or outwardly every predetermined distance from the center thereof to reinforce strength or plural ribs 201 formed along the circumferential direction.
Also, as shown in FIG. 3, the tub 2 is injection-molded. More specifically, an injection-molding material inlet 410 which defines a gate part after molding is formed in a metal mold 400 and an injection part 270 is provided in the mold-injection opening 410 to allow an injection-molding material injected therein, thereby injecting the injection-molding material into the metal mold.
However, the conventional drum washing machine, as shown in FIG. 3, has a problem that the inflow of injection-molding material is not smooth, because the injection direction of the injection-molding material injected through the gate part and the inflow direction for defining a rear wall of the tub 2 are too much perpendicularly bent in injection-molding the rear wall of the tub. Moreover, the conventional drum washing machine has another problem that inferiority of injection-molding may arise in an outer surface of the rear wall of the tub 2 due to the above unsmooth inflow of the injection-molding material.